Grantee Research Project Results

A Study of the Aqueous Phase Processing of Organic Aerosols through Carbon Stable Isotope Analysis

EPA Grant Number: FP917803
Title: A Study of the Aqueous Phase Processing of Organic Aerosols through Carbon Stable Isotope Analysis
Investigators: Napolitano, Denise Carol
Institution: Arizona State University
EPA Project Officer: Lee, Sonja
Project Period: September 1, 2015 through August 31, 2018
Project Amount: $132,000
RFA: STAR Graduate Fellowships (2015) RFA Text | Recipients Lists
Research Category: Academic Fellowships

Objective:

Atmospheric particles affect human health by causing respiratory stress and disease and also influence our climate due to the scatter and absorption of solar radiation. Existing atmospheric models underestimate concentrations of aerosol particulate matter and create gaps in our understanding of the atmospheric organic carbon budget, especially in relation to aqueous phase reactions that occur in fog and clouds. In this project, stable carbon isotopes will be used to track the progress of atmospheric aqueous phase reactions to determine if these processes affect particulate matter concentrations.

Approach:

Aqueous and gas-phase secondary organic aerosol-forming reactions will be studied by investigating the chemistry of small, semi-volatile reactive compounds, such as dicarboxylic acids. Authentic samples of fog will be photooxidized in laboratory simulations, and the isotopic composition of the resulting dicarboxylic acids will be measured. Using knowledge of the isotopic composition of primary aerosols and gas-phase volatile organic compounds, the pathways of dicarboxylic acid formation will be determined, and their precursors and sources will be ascertained. Future field campaigns will involve the collection of particulate matter, fog, and gas phase samples. Observed changes in the isotopic composition of dicarboxylic acids in all phases as fog forms, matures, and evaporates will aid in determining how these acids are processed in both gas-phase and aqueous-phase photochemical aging. The effect of dicarboxylic acid formation on particulate matter mass will also be investigated.

Expected Results:

Due to the nature and behavior of small dicarboxylic acids that are common constituents of atmospheric samples, it is expected that reactions forming secondary organic aerosols in the aqueous phase will result in an increase in aerosol particulate matter, since it is likely that their precursors originate in the gas phase. The outcomes of my research will provide clarification of the atmospheric organic carbon budget that could ideally be applied to total organic carbon and help ameliorate uncertainties in atmospheric models. Modeling improvements will be implemented through integration with current atmospheric models that account for interactions of cloud and fog water with gas and particle phases.

Supplemental Keywords:

Atmosphere, climate, health, particulate matter, secondary organic aerosol, carbon isotopes, cloud, fog

Progress and Final Reports:

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.